The top U.S. and NATO commander in Afghanistan, U.S. Marine Corps General John Allen, says coalition forces remain on track to deny al-Qaida safe haven in the country, despite recent setbacks.

Allen testified Tuesday before the House Armed Services Committee panel, whose lawmakers disagree over the pace of America's troop withdrawal from Afghanistan.

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It was Allen's first appearance before the panel since a U.S. soldier allegedly shot and killed 16 Afghan villagers on March 11. Allen's testimony also follows violent protests that erupted last month after the inadvertent burning of Korans at a U.S. air base. The U.S. commander told lawmakers that 32 Afghans were killed in those riots.

Allen said that in any counter-insurgency situation, there will be successes and setbacks - often at the same time and in the same space. But he said that ties between coalition forces and Afghan national forces remain strong.

"I believe the campaign is on track," said Allen. "We are making a difference. I know this and our troops know this."

Allen said morale among U.S. forces is high, despite what he called several recent "heart-wrenching" events.

"These troops are focused on a mission," he said. "Ten years into this conflict, they are as professional as we have ever seen."

The committee's chairman, Rep. Howard "Buck" McKeon, a California Republican, called the incident in which a U.S. Army staff sergeant allegedly took up arms against Afghan civilians last week an isolated and criminal act that should be prosecuted to the full extent of the law. But, he said, this and other events are not representative of the commitment of U.S. forces.

"These exceptional incidents are not reflective of the hundreds of thousands of U.S. soldiers, sailors, airmen and Marines who have served honorably in Afghanistan," said McKeon. "Nor are they reflective of the many thousands of Afghan soldiers who are being trained and are helping to secure Afghanistan today."

McKeon said he is troubled by President Barack Obama's decision to withdraw U.S. forces from Afghanistan, saying it might interfere with the president's own strategy.

The top Democrat on the committee, Rep. Adam Smith of Washington state, said the point of the president's strategy is to transfer the responsibility of providing security from coalition forces to Afghan national forces.

"We simply cannot say, 'Well, we are never going to leave, we are going to stay because we are fearful, because if people think we are going to leave, that, therefore, gives them an advantage,'" said Smith. "The truth is it also gives them an advantage, if we leave in the minds of the Afghan people that we are never going to leave."

Smith said that Americans want to see U.S. troops come home, and that they want Afghans to be in charge of their own security and their own government.

General Allen's testimony comes at a time when several lawmakers - Republicans and Democrats - increasingly say that the financial and human costs of the long war in Afghanistan are too high.

White House spokesman Jay Carney said Tuesday that he cannot provide any numbers on the pace of the U.S. pullout. Carney said although Afghanistan would be a topic of intense discussion at next month's NATO summit in Chicago, people should not expect a new announcement about troop withdrawals.﻿